This project will continue to investigate whether the somatosensory cortex of the monkey is specialized so as to reflect the differential roles of the spinal cord afferent systems in tactile discrimination. Stump-tail macaques will be trained on a series of tactile problems, one set of which is mediated by the dorsal columns, and another set of which is mediated by multiple afferent systems. The animals will then undergo surgery for ablations of either area 1 or area 2 of the somatosensory cortex, followed by postoperative re-testing. The data will be analyzed for any differential effects by these lesions on the two types of tactile discrimination, and compared with earlier results after lesions to area 3 and SS II. We expect that the proposed damage to areas 1 and/or 2 will impair the dorsal column functions more than the other discriminative tasks, in contrast to the effects of lesions in area 3 and SS II. In 3 other monkeys, we will finish studying the effect of analgesics in dissociating the sensation of skin warming from that of skin cooling.